Not too sure what your doing there to be honest, but if you just set the iframe style attribute to nothing and call using a js function like I have below, am sure it will all work good for you 
<script language="javascript">
function showIframe(){
var iframeStyle = document.getElementById("MyIframe").style
if(iframeStyle.display == ""){
iframeStyle.display = "none";
return;
}
iframeStyle.display = "";
return
}
<img onclick="showIframe()" src="somesource.gif">
<iframe id="MyIframe" width="100%" height="300" style="display: none"></iframe>